Whenever a new lens is released, we almost always see those infamous MTF charts posted along with the product images. But what exactly are MTF charts? What are they? Why are they a thing? How do you read them? And why should you care?
In this video, photographer Dustin Abbot goes into a deep dive on MTF charges to explain exactly what they are and how they’re of benefit to photographers. While he does go quite detailed into the charts, it’s an easy to understand analysis of what they are.
Essentially, MTF charts are lens performance charts. They give you some indication of how a lens is expected to perform based on various situations such as high vs low-resolution sensors or wide-open vs stopped down to f/8. Not all manufacturers display exactly the same information with the same variables, so using the charts to theorise about one lens from one company vs another lens from a different company might not always give you a realistic comparison, but independently, they should give you some idea of what to expect from each lens itself.
Ideally, the MTF charts are made from examining a number of samples from a given model of lens to produce an average for that lens. It won’t be identical to the lens you ultimately buy. Your lens might be above average or below average in real-world testing compared to the charts. If it’s above, count yourself lucky. If it’s well below what the chart suggests, though, you might have a dud and will definitely want to call customer service.
What MTF charts can’t do is tell you the absolute sharpness and clarity of a lens in all conditions. Even different lighting conditions can make a lens present softer, with reduced contrast or more chromatic aberration than the charts might suggest. Remember, the charts are made in consistent ideal lab conditions. Not out in the real world where things are more random and constantly changing.
When all’s said and done, an MTF chart might be a fancy statistic shown off by some manufacturers as a selling point of how sharp they are, but as Dustin says, it really just gives you a baseline of how you can expect the lens to perform. It’s just one factor and shouldn’t be the sole reason for buying a lens. You’ll also want to look at sample photos and try the lens out in person if you can before you choose to buy.
How much attention do you pay to MTF charts when you buy a new lens? Do you even know what they are?